Medical professionals who use needle devices to treat patients face the risk of being pierced by contaminated needles. Widespread concern for various blood born pathogens, such as the AIDS virus, has led to advancements in needle devices. Many needle devices in the art now provide a mechanism for retracting the needle into an enclosure after the needle is removed from a patient. Once the needle is retracted in these devices, the medical professional can safely handle and dispose of the device. Over time, advancements have made retractable needle devices easier and safer to use. Some needle devices now have elements that prevent removal or reuse of contaminated needles once they are retracted into an enclosure.
Safety features have become desirable in a variety of needle devices, including devices that inject medication from pre-filled cartridges (i.e. “cartridge injectors”). In some cases, safety features have been retrofitted into prior art designs, or designed to accommodate existing parts, so as to retain existing components and minimize the need for new components. These changes have generally been unfavorable in terms of both design concerns and cost. In some cartridge injectors, the safety components are not compatible with commercially available medicine cartridges, and redesigned cartridges must be used in the device. In other cartridge injectors, the addition of safety features has added size and bulk to the device, making the device less desirable for use.